A side air bag device M0 of this kind in the prior art is constructed, as shown in FIG. 38, to include an air bag 1 mounted on the peripheral edge of a door opening W inside of the compartment of the body of a vehicle, and an inflator 7 for discharging an expanding gas to inflate the air bag 1.
The air bag 1 is composed of a plurality of expansion chambers to be expanded into bags, uninflatable flat walls 4, 4 arranged at the front and rear sides of the vehicle in the expansion chamber 2, and a pipe insert 5 into which a pipe 6 for feeding the expanding gas from the inflator 7 is to be inserted.
The expansion chamber 2 is partitioned by joints 3 which are formed by stitching the inner side wall and the outer side wall of the air bag 1 generally vertically from their respective upper to lower edges.
When this air bag 1 is to be inflated, the expanding gas is fed from the inflator 7 via the pipe 6 and through its not-shown through-holes to inflate the individual expansion chambers 2.
As these expansion chambers 2 are inflated, there is established a tension along a line L--L which extends from the lower side to the obliquely upper side of the peripheral edge of the door opening W of the air bag 1, so that the air bag 1 can restrain the head of a passenger reliably by the tension line L--L, even when the air bag 1 is impacted by the passenger's head.
Here, the air bag 1 is mounted on the generally L-shaped portion or the peripheral edge of the door opening W. Unless the tension is established on the tension line L--L at the time of expansion, the air bag 1 will merely move but fail to restrain the passenger's head properly even when it is impacted by the head.
In the air bag 1 of the prior art, however, the expanding gas is fed to the expansion chambers 2 which are partitioned in plurality, and the expanding gas from the inflator 7 is fed via the long pipe 6 sequentially into the individual expansion chambers 2. Since the pipe 6 is inserted into the air bag 1, the air bag 1 is mounted in a bulky state within the vehicle to enlarge the size of the side air bag device M0.
In the air bag 1 of the prior art, on the other hand, the expanding gas is fed to the expansion chambers 2 which are partitioned in plurality by the joints 3. The expanding gas from the inflator 7 is fed via the long pipe 6 sequentially into the individual expansion chambers 2 so that the pressure-loss of the expanding gas is high. Unless the inflator 7 has a high output, the time period for completing the expansion of the air bag 1 until the tension is exhibited on the tension line L--L is prolonged.
Moreover, the air bag 1 of the prior art is folded along the pipe insert 5 on the peripheral edge of the opening W. The individual joints 3, as formed by stitching the inner side wall and the outer side wall to form the plural expansion chambers 2, are formed in the folding direction perpendicular to the pipe insert 5. However, the stitching threads forming the individual joints 3 overlap one another when the air bag 1 is folded, and the joints 3 per se forming the expansion chambers 2 are numerous, so that the air bag 1 cannot be folded compactly, which makes it difficult to retain sufficient space for the bag itself.
The present invention has been conceived to solve the above-specified problems, and has as its object to provide an air bag for a side air bag device, which can reduce the size and weight of the device while retaining the tension line at the time of expansion.
Another object of the invention is to provide an air bag for a side air bag device, which can suppress the pressure loss of the expanding gas and employ an inflator of a low output.
Still another object of the invention is to provide an air bag for a side air bag device, which can be folded compactly.